The studies proposed here are directed towards the amino acid sequence determination of a number of polypeptide chains from hemoglobins with unusual functional properties. Initial focus will be on the ontogeny of hemoglobins in the bullfrog tadpole. We have identified four major hemoglobin components in pre-metamorphic tadpoles. Two of these are predominant in the youngest tadpoles and are gradually replaced by two more hemoglobins in older tadpoles. These two groups of hemoglobins, according to the work of Broyles and Frieden arise from two different cell populations (in the kidney and liver). I wish to identify the ontogeny of the different polypeptide chains and to determine each of their primary structures. We have already determined that a total of 4 unique Beta chains and at least 3 unique alpha chains are present in the 4 components. Since we have found that the hemoglobins have quite different functional properties we wish to determine, by sequence analysis, the molecular basis for these functional differences. We also plan to determine the distribution of these polypeptide chains in the different cell populations.